Sensor systems and methods for detecting conveyor tension in a mining system

ABSTRACT

A conveyor system that includes a sprocket, a conveyor element, a sensor, a tensioning system, and an electronic processor. The conveyor element is coupled to the sprocket to move around the sprocket. The sensor is positioned adjacent to the sprocket and configured to generate an output signal indicative of a detection of the conveyor element. The electronic processor is coupled to the sensor and to the tensioning system. The electronic processor is configured to receive the output signal from the sensor, estimate a trajectory of the conveyor element based on the output signal, determine a value for slack distance based on the estimated trajectory of the conveyor element, and control the tensioning system based on the value for slack distance.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/161,607, filed Oct. 16, 2018, which claims the benefit of U.S.Provisional Patent Application No. 62/573,552, filed Oct. 17, 2017, theentire content of each of which is hereby incorporated by reference.

BACKGROUND

This invention relates to methods and systems used for detecting tensionof a conveyor, such as an armored face conveyor (“AFC”) or a beam stageloader (“BSL”).

SUMMARY

In one embodiment, the invention provides a conveyor system thatincludes a sprocket, a conveyor element, a sensor, a tensioning system,and an electronic processor. The conveyor element is coupled to thesprocket to move around the sprocket. The sensor is positioned adjacentto the sprocket and configured to generate an output signal indicativeof a detection of the conveyor element. The electronic processor iscoupled to the sensor and to the tensioning system. The electronicprocessor is configured to receive the output signal from the sensor,estimate a trajectory of the conveyor element based on the outputsignal, determine a value for slack distance based on the estimatedtrajectory of the conveyor element, and control the tensioning systembased on the value for slack distance.

In another embodiment, the invention provides a computer-implementedmethod for controlling tension in a conveyor element of a conveyorsystem. The conveyor system includes the conveyor element, a sprocket, asensor, a tensioning system, and a processor. The method includesreceiving, at the processor, an output signal from a sensor positionedadjacent to the sprocket, estimating, using the processor, a trajectoryof the conveyor element based on the output signal from the sensor,determining, using the processor, a value for slack distance based onthe estimated trajectory of the conveyor element, and controlling, usingthe processor, the tensioning system based on the value for slackdistance.

In another embodiment, the invention provides a controller forcontrolling tension in a conveyor element of a conveyor system. Thecontroller includes a non-transitory computer readable medium and aprocessor. The controller includes computer executable instructionsstored in the computer readable medium for controlling the operation ofthe conveyor system to receive an output signal from a sensor positionedadjacent to a sprocket, estimate a trajectory of a conveyor elementbased on the output signal from the sensor, determine a value for slackdistance based on the estimated trajectory of the conveyor element, andcontrol a tensioning system based on the value for slack distance.

In another embodiment, the invention provides a conveyor system thatincludes a sprocket, a conveyor element, a sensor, a tensioning system,and an electronic processor. The conveyor element is coupled to thesprocket to move around the sprocket. The sensor is positioned adjacentto the sprocket. The sensor is configured to generate an analog outputsignal indicative of a distance between the sensor and the conveyorelement. The electronic processor is connected to the sensor and thetensioning system. The electronic processor is configured to receive theanalog output signal from the sensor, determine whether a value for theanalog output signal is within a predetermined range, determine atension correction amount based on the analog output signal when theanalog output signal is outside the predetermined range, and control thetensioning system based on the tension correction amount.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of the configuration and arrangement of components set forthin the following description or illustrated in accompanying drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein are for the purpose ofdescription and should not be regarded as limiting. The user of“including,” “comprising,” or “having” and variations thereof herein aremeant to encompass the items listed thereafter and equivalents thereofas well as additional items. Unless specified or limited otherwise, theterms “mounted,” “connected,” “supported,” and “coupled” and variationsthereof are used broadly and encompass both direct and indirectmountings, connections, supports, and couplings.

In addition, it should be understood that embodiments of the inventionmay include hardware, software, and electronic components or modulesthat, for purposes of discussion, may be illustrated and described as ifthe majority of the components were implemented solely in hardware.However, one of ordinary skill in the art, and based on a reading ofthis detailed description, would recognize that, in at least oneembodiment, the electronic based aspects of the invention may beimplemented in software (e.g., stored on non-transitorycomputer-readable medium) executable by one or more processing units,such as a microprocessor and/or application specific integrated circuits(“ASICs”). As such, it should be noted that a plurality of hardware andsoftware based devices, as well as a plurality of different structuralcomponents may be utilized to implement the invention. For example,“servers” and “computing devices” described in the specification caninclude one or more processing units, one or more computer-readablemedium modules, one or more input/output interfaces, and variousconnections (e.g., a system bus) connecting the components.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a conveyor system.

FIG. 2 is a block diagram of a control system for the conveyor system ofFIG. 1.

FIG. 3 illustrates a sensor assembly of the control system of FIG. 2,according to an embodiment of the invention.

FIG. 4 illustrates an underside perspective view of the analog outputsensor of FIG. 3.

FIG. 5 is a process for maintaining tension in the conveyor system ofFIG. 1 using the sensor assembly of FIG. 3.

FIG. 6 illustrates a sensor assembly of the control system of FIG. 2,according to an embodiment of the invention.

FIG. 7 is a chart illustrating relationships between differentcombinations of output signals from a sensor assembly and acorresponding conveyor state.

FIG. 8 is a process for maintaining tension in the conveyor system ofFIG. 1 using the sensor assembly of FIG. 6.

FIG. 9 illustrates a sensor assembly of the control system of FIG. 2,according to an embodiment of the invention.

FIGS. 10A-10D illustrate chain trajectories for the conveyor system ofFIG. 1.

FIG. 11 illustrates a sensor assembly of the control system of FIG. 2,according to an embodiment of the invention.

FIG. 12 is a process for maintaining tension in the conveyor system ofFIG. 1 using the sensory assembly of FIG. 11.

FIG. 13 is a process for analyzing whether the conveyor system of FIG. 1is approaching an unacceptable tension range.

DETAILED DESCRIPTION

Conveyor systems are typically used in mining operations to transportmaterial. In longwall mining, for example, the beam stage loaderconveyor system is used to transport the mined coal from the armoredface conveyor (“AFC”) to the main conveyor that transports the coal tothe surface. FIG. 1 illustrates a schematic diagram of a conveyor system100 used for transporting mineral material. As shown in FIG. 1, theconveyor system 100 includes a conveyor 105, a first conveyor shaft 110,a second conveyor shaft 115, a first conveyor chain 120, and a secondconveyor chain 125. In some embodiments, the conveyor 105 may includemore or fewer conveyor chains. In some embodiments, the conveyor chains120, 125 are replaced by a different conveyor element such as a belt, orthe like. The conveyor system 100 is at least partially supported by aframe 130 (see FIG. 3). In some embodiments, the frame 130 includes afirst end portion to support the first conveyor shaft 110, a second endportion to support the second conveyor shaft 115, and a conveyor pan tosupport the first and second conveyor chains 120, 125 or other conveyorelement. The first conveyor chain 120 and the second conveyor chain 125(e.g., the conveyor elements) are positioned around the first conveyorshaft 110 and the second conveyor shaft 115 to form the conveyor 105. Asshown in FIG. 1, the first conveyor chain 120 is positioned around afirst end of the first conveyor shaft 110 and around a first end of thesecond conveyor shaft 115 while the second conveyor chain 125 ispositioned around a second end of the first conveyor shaft 110 andaround a second end of the second conveyor shaft 115.

Each conveyor shaft 110, 115 includes a sprocket for each conveyorelement. The sprocket engages the conveyor element to turn the conveyorelement around the sprocket. In the illustrated embodiment, eachconveyor shaft 110, 115 includes two sprockets. In the illustratedembodiment, a first sprocket 132 on the first conveyor shaft 110 engagesthe first conveyor chain 120 and a second sprocket 135 on the firstconveyor shaft 110 engages the second conveyor chain 125. Similarly, athird sprocket 140 on the second conveyor shaft 115 engages the firstconveyor chain 120 and a fourth sprocket 145 on the second conveyorshaft 115 engages the second conveyor chain 125. The sprockets 132, 135,140, 145 are driven by one or more drive mechanisms (e.g., motors),which causes movement of the chains 120, 125 around the first conveyorshaft 110 and the second conveyor shaft 115 such that the conveyor 105transports the mining material. In the illustrated embodiment, theconveyor 105 includes flightbars 150 that assist in transporting themining mineral with the conveyor 105. As shown in FIG. 1, the flightbarsare supported by the first and second conveyor chains 120, 125. In someembodiments, the conveyor 105 also includes chain covers to cover andprotect the conveyor chains 120, 125.

In the illustrated embodiment, to conveyor system 100 is part of thebeam stage loader of a longwall mining system. In other embodiments,however, the conveyor system 100 may be part of a different miningmachine such as, for example, an armored face conveyor, a feederbreaker, the main conveyor in a longwall mining system, and the like.

FIG. 2 illustrates a block diagram of a control system 200 for theconveyor system 100. The control system 200 is configured to maintainthe conveyor system 100 within an adequate tension range. When theconveyor 105 is improperly tensioned (e.g., the tension of the conveyor105 is outside of an adequate tension range), the mining material maynot be efficiently transported. Additionally, the conveyor 105 may bemore susceptible to wear, malfunction, or a combination thereof when theconveyor 105 is improperly tensioned. The adequate tension range mayvary based on, for example, the material being transported by theconveyor 105, the type of conveyor element utilized, the speed at whichthe conveyor 105 is operated, or combinations thereof. For example,adequate tension for the conveyor 105 corresponds to an amount oftension that is not too high or too low. Tension that is too high in theconveyor 105 could damage the conveyor 105 as more material is added tothe conveyor 105 (e.g., could cause a breakage of the conveyor 105).Tension that is too low in the conveyor 105 can cause slack chain (e.g.,distance between a sprocket and a conveyor chain). An adequate tensionin the conveyor corresponds to circumstances where, given the currentoperational state of the conveyor 105, the tension is not too high ortoo low.

As shown in FIG. 2, the control system 200 includes a sensor assembly205, a tensioning system 210, and an electronic processor 215. Thesensor assembly 205 is configured to generate an output signal based onits detection of the conveyor elements (e.g., the first and secondconveyor chains 120, 125). The electronic processor 215 is, for example,a controller that includes a processing unit and a memory. The memorycan be a non-transitory computer-readable medium operable for storingexecutable instructions that can be retrieved by the processor andexecuted by the processor. The executable instructions correspond to thevarious control techniques and processes described herein. The termselectronic processor and controller are used interchangeably herein.

The tensioning system 210 changes the distance between the firstconveyor shaft 110 and the second conveyor shaft 115. The distancebetween the first conveyor shaft 110 and the second conveyor shaft 115set the tension of the conveyor 105. As the distance between the firstand the second conveyor shafts 110, 115 increases, the tension of theconveyor 105 also increases. Conversely, when the distance between thefirst and second conveyor shafts 110, 115 decreases, the tension of theconveyor 105 decreases. In some embodiments, the tensioning system 210includes a first hydraulic cylinder coupled to the first conveyor shaft110 and a second hydraulic cylinder coupled to the second conveyor shaft115. In other embodiments, the tensioning system 210 may include more orfewer hydraulic cylinders. The hydraulic cylinders change the positionof the respective conveyor shafts 110, 115 to thereby change thedistance between the first and second conveyor shafts 110, 115. Asdiscussed above, when the distance between the first and the secondconveyor shafts 110, 115 changes, the tension of the conveyor 105 alsochanges. The hydraulic cylinders may be driven by, for example, ahydraulic system.

As shown in FIG. 2, the electronic processor 215 is coupled to thesensor assembly 205 and the tensioning system 210. In particular, theelectronic processor 215 receives the output signal(s) from the sensorassembly 205, determines whether the conveyor 105 is within an adequatetension range based on the output signal(s), and activates thetensioning system 210 when the conveyor 105 is outside the adequatetension range, or when the electronic processor 215 predicts that theconveyor 105 will be outside the adequate tension range withoutpreventative action by the tensioning system 210. In one embodiment, thetensioning system 210 includes a hydraulic and/or electronic system todrive the hydraulic cylinders. In such an embodiment, the electronicprocessor 215 transmits an activation signal to the tensioning system210 when the distance between the first and the second conveyor shafts110, 115 is to be changed.

FIG. 3 illustrates an embodiment 300 of the sensor assembly 205. In theillustrated embodiment 300, the sensor assembly 205 includes an analogoutput sensor 310 for each conveyor element (i.e., each conveyor chain120, 125). For example, a first analog output sensor 310 detects acharacteristic of the first conveyor chain 120 and a second analogoutput sensor 310 detects a characteristic of the second conveyor chain125. Although FIG. 3 illustrates only a single analog output sensor 310positioned adjacent the first sprocket 132 to detect a characteristic ofthe first conveyor chain 120, a second analog output sensor 310 issimilarly positioned adjacent the second sprocket 135 or the fourthsprocket 145 to detect a characteristic of the second conveyor chain125. In some embodiments, additional analog output sensors may bepositioned adjacent the third sprocket 140 to obtain a secondmeasurement of the tension of the first conveyor chain 120, and anothersensor may be positioned adjacent the fourth sprocket 145 to obtain asecond measurement of the tension of the second conveyor chain 125. Asshown in FIG. 3, the analog output sensor 310 is supported by the frame130 near the discharge point of the first conveyor chain 120 (e.g., theconveyor element).

The analog output sensor 310 may be, for example, an ultrasonic sensor,an IR sensor, a magnetometer, and the like. The analog output sensor 310generates an analog output signal indicative of a distance between theanalog output sensor 310 and the first conveyor chain 120. Inparticular, the analog output signal has a variable output range suchas, for example, 0-10V, 200-500 MHz, 100-300 μF, and the like. The value(e.g., magnitude) of the analog output signal is linearly related to thedistance between the analog output sensor 310 and the first conveyorchain 120. In the illustrated embodiment, the analog output signalincreases in value as the distance between the analog output sensor 310and the first conveyor chain 120 decreases. That is, the analog outputsensor 310 outputs a minimum value when the first conveyor chain 120 ispositioned at an edge 320 of a detection area 325 of the analog outputsensor 310. The analog output sensor 310 thereby gives at least anindirect measure of the slack distance of the first conveyor chain 120.The electronic processor 215 can then determine whether the tensioningsystem 210 is to be activated (e.g., whether the conveyor 105 needs tochange its tension). Because the analog output sensor 310 generates avariable output signal, the control by the tensioning system 210 may bemore precise than, for example, using a switch-like detector for theslack distance of the conveyor chains 120, 125. Additionally, a singleanalog output sensor 310 generates more precise information than usingswitch-like detectors that only generate binary outputs. Accordingly, byusing the analog output sensor 310, a reduction of the overall number ofcomponents may be achieved. In some embodiments, the analog outputsensor 310 utilizes a time-of-flight measurement to generate the analogoutput signal. In other embodiments, however, different measurementtechniques are utilized to generate the analog output signal. FIG. 4illustrates another perspective of the placement for the analog outputsensor 310. In particular, FIG. 4 illustrates a underside perspectiveview of the analog output sensor 310. In the illustrated embodiment, theanalog output sensor 310 is an ultrasonic sensor configured to generatea variable output signal indicative of the distance between the analogoutput sensor 310 and the first conveyor chain 120.

FIG. 5 is a flowchart illustrating a method 350 of maintaining theconveyor system 100 at an adequate tension using the embodiment 300 ofthe sensor assembly 205 in either the placement shown in FIG. 3 or theplacement shown in FIG. 4. In STEP 355, the analog output sensor 310generates an analog output signal indicative of a distance between theanalog output sensor 310 and the first conveyor chain 120. Theelectronic processor 215 receives the analog output signal (STEP 360)and determines whether the analog output signal is within an acceptablerange (STEP 365). The acceptable range is predetermined and stored. Theelectronic processor 215 accesses the acceptable range and compares amagnitude of the analog output signal to the acceptable range. In someembodiments, the electronic processor 215 may, for example, consult alook-up table storing different magnitudes of the analog output signaland indicating whether the particular magnitude or range of magnitudesis acceptable. The acceptable range for the analog output signalpreferably falls approximately halfway through the possible outputs ofthe analog output sensor 310. For example, when the analog output sensor310 has an output range of approximately 0V-10V, the acceptable rangemay be, for example, 4V-6V.

When the analog output signal is within the acceptable range, theelectronic processor 215 continues to monitor the first conveyor chain120 and receiving the analog output signal from the analog output sensor310. On the other hand, when the analog output signal is outside theacceptable range, the electronic processor 215 determines a correctionamount (STEP 370). The correction amount indicates an amount that theconveyor 105 needs to increase or decrease in tension. Because theanalog output signal provides a variable output signal, the magnitude ofthe analog output signal can be used to more precisely determine anamount by which the tension of the conveyor 105 is to be changed.

In one embodiment, the electronic processor 215 determines thecorrection amount by calculating a difference between the analog outputsignal and the acceptable range. For example, when the analog outputsignal is 2V (e.g., indicating that the first conveyor chain 120 isunder-tensioned), the electronic processor 215 may determine thecorrection amount by calculating the difference between 4V (e.g., thelowest value in the acceptable range) and the analog output signal of2V. The electronic processor 215 calculates the difference to beapproximately 2V.

In some embodiments, the electronic processor 215 converts thedifference of the acceptable range and the analog output signal into acorresponding change in distance between the first conveyor shaft 110and the second conveyor shaft 115. In the example above, the electronicprocessor 215 may then determine the difference of 2V to correspond to achange of approximately 10 inches between the first conveyor shaft 110and the second conveyor shaft 115. The electronic processor 215 mayassign a direction to the correction amount to indicate whether thetensioning system 210 is to increase the tension of the conveyor 105 orreduce the tension of the conveyor 105. For example, when the analogoutput signal indicates that the conveyor 105 is over-tensioned, theelectronic processor 215 may set the correction amount to a negativevalue (for example, −2V) to indicate that the tensioning system 210 isto decrease the tension of the conveyor 105.

After determining the correction amount, the electronic processor 215sends a control signal to activate the tensioning system 210 based onthe correction amount (STEP 375). In particular, the electronicprocessor 215 sends an activation signal to the tensioning system 210such that the tensioning system 210 changes the distance between thefirst conveyor shaft 110 and the second conveyor shaft 115 by thecorrection amount. In some embodiments, the tensioning system 210 mayinclude a timer that sets a duration during which the tensioning system210 is activated to change the distance between the first conveyor shaft110 and the second conveyor shaft 115. In such embodiments, thecorrection amount may correspond to a duration of the timer. In theexample above where the difference between the analog output signal andthe acceptable range is 2V, the correction amount may be, for example,10 seconds. The duration of the timer (e.g., the correction amount) may,in such embodiments, be based on the average speed of the tensioningsystem 210. The speed of the tensioning system 210 may be apredetermined amount stored (or accessed from memory) by the electronicprocessor 215. The electronic processor 215 then returns to STEP 355 andcontinues to monitor the analog output signal with respect to theacceptable range.

FIG. 6 illustrates another embodiment 400 of the sensor assembly 205. Inthe illustrated embodiment 400, the sensor assembly 205 includes twosets of proximity sensors, 405, 410. The first set 405 of proximitysensors is positioned on a block side of the conveyor 105 (e.g., to theoutside of the first sprocket 132). The first set 405 of proximitysensors includes a first proximity sensor 415, a second proximity sensor420, and a third proximity sensor 425. The second set 410 of proximitysensors is positioned on a walk side of the conveyor 105 (e.g., to theinside of the first sprocket 132). The second set 410 of proximitysensors includes a fourth proximity sensor 430, a fifth proximity sensor435, and a sixth proximity sensor 440. In the illustrated embodiment,each of the proximity sensors 415-440 is energized as the first conveyorchain 120 (or a flightbar 150) is detected. In the illustrated example,the proximity sensors 415-440 are inductive proximity switch sensorswith an approximate detection range of 40 mm. Accordingly, each of theproximity sensors 415-440 generates a binary output signal that istransmitted to the electronic processor 215. In some embodiments, theproximity sensors 415-440 may be longer range IR, lasers, and the like.As explained in further detail below, the electronic processor 215determines whether the tensioning system 210 needs to be activated basedon the combination of binary output signals received from the first andsecond sets 405, 410 of proximity sensors. In other embodiments, thefirst and second sets 405, 410 of proximity sensors may include more orfewer proximity sensors. In the illustrated embodiment, the precision ofthe embodiment 400 of the sensor assembly 205 is improved by increasingthe number of proximity sensors 415-440 and decreasing a distancebetween each of the proximity sensors 415-440.

As shown in FIG. 6, the first, second and third proximity sensors 415,420, 425 are arranged linearly, with the first proximity sensor 415positioned closest to the first sprocket 132 and the third proximitysensor 425 positioned furthest from the first sprocket 132. Similarly,the fourth, fifth, and sixth proximity sensors 430, 435, 440 arearranged linearly, with the fourth proximity sensor 430 positionedclosest to the first sprocket 132 and the sixth proximity sensor 440positioned furthest from the first sprocket 132. The first and fourthproximity sensors 415, 430 are positioned at a first height (e.g., adistance from the first sprocket 132 or support frame). Similarly, thesecond and the fifth proximity sensors 420, 435 are positioned at asecond height different than the first height, and the third and thesixth proximity sensors 425, 440 are positioned at a third heightdifferent than the first and second heights. In the illustratedembodiment, the first height corresponds to a slack distance of 0 mm,the second height corresponds to a slack distance of 75 mm, and thethird height corresponds to a slack distance of 150 mm. That is, whenthe first conveyor chain 120 is at the first height, the first conveyorchain 120 has 0 mm of slack distance, when the first conveyor chain 120is at the second height, the first conveyor chain 120 has 75 mm of slackdistance, and when the first conveyor chain 120 is at the third height,the first conveyor chain 120 has 150 mm of slack distance. Because thefirst set 405 of proximity sensors and the second set 410 of proximitysensors are positioned on opposite sides of the first sprocket 132, acombination of the outputs of each proximity sensor provides moreaccurate information about the slack distance of the first conveyorchain 120 and accordingly, regarding the tension of the conveyor 105.

FIG. 7 illustrates an exemplary chart indicating the differentcombinations of sensor outputs, and what each combination indicates withrespect to a state of the tension of the conveyor 105. The exemplarychart illustrates an “X” where the signal from that particular sensor isinconsequential to the determination of the state of the conveyor 105.Because the proximity sensors in each set 405, 410 are arrangedlinearly, the signal from the proximity sensor that is furthest from thesprocket 132 indicates the slack distance of the first conveyor chain120, and therefore the signal from the proximity sensors that are closerto the sprocket 132 are not taken into consideration to determine thetension state of the conveyor 105. For example, when the second sensor420 outputs a positive signal (e.g., indicating that the first conveyorchain 120 is within the detection range of the second sensor), theoutput of the first sensor 415 is inconsequential to determining thetension state of the conveyor 105 and is, therefore, set to “X.”

Based on the illustrated chart, an over-tensioned state of the conveyor105 is indicated when a positive signal is received from the firstsensor 415 and the fourth sensor 430 (e.g., the first conveyor chain 120is within the detection range of the first sensor 415 and the fourthsensor 430), and a negative signal is received from the second, third,fifth, and sixth sensors 420, 425, 435, 440 (e.g., the first conveyorchain 120 is outside the detection range of the second, third, fifth,and sixth sensors). As also illustrated in the exemplary chart, anunder-tensioned state of the conveyor 105 is indicated by six differentoutput combinations from the proximity sensors 415-440. Additionally, byutilizing the sensor arrangement of FIG. 6, abnormal conditions of theconveyor 105 may also be detected. In the illustrated embodiment,abnormal conditions of the conveyor 105 may be indicated when, forexample, the first sensor 415 outputs a positive signal, but the secondset 410 of sensors output negative signals, and separately, when thefourth sensor 430 outputs a positive signal, but the first set 405 ofsensors output negative signals. Such outputs may indicate, for example,that the conveyor is bent or encountering an abnormal load condition. Alack of positive signal from the first set 405 or the second set 410 ofproximity sensors may also indicate that one of the proximity sensors ismalfunctioning.

FIG. 8 illustrates a method 450 of maintaining the conveyor system 100at an adequate tension using the embodiment 400 of the sensor assembly205. In STEP 455, the electronic processor 215 receives output signalsfrom each of the proximity sensors 415-440. The electronic processor 215then identifies an applicable combination of outputs from the proximitysensors 415-440 (STEP 460). For example, the electronic processor 215may determine which combination of outputs from the exemplary chart ofFIG. 7 matches the proximity output signals received by the electronicprocessor 215. In some embodiments, the electronic processor 215 mayaccess a look-up table similar to the exemplary chart of FIG. 7 frommemory. In other embodiments, however, the electronic processor 215 mayapply rules and thresholds in software to determine the combination ofoutputs that matches the output signals received by the electronicprocessor 215. The electronic processor 215 then determines a tensionstate of the conveyor 105 based on the combination of proximity outputsignals received by the electronic processor 215 (STEP 465).

When the electronic processor 215 determines that the conveyor 105 isover-tensioned, the electronic processor 215 activates the tensioningsystem 210 to decrease the tension of the conveyor 105 (STEP 470). Onthe other hand, when the electronic processor 215 determines that theconveyor 105 is under-tensioned, the electronic processor 215 activatesthe tensioning system 210 to increase the tension of the conveyor 105(STEP 475). In some embodiments, the electronic processor 215 may alsodetect abnormal conditions of the conveyor 105 based on the proximityoutput signals received by the electronic processor 215. When theelectronic processor 215 detects an abnormal condition, an alarm isgenerated (STEP 480). In some embodiments, the alarm may be communicatedto an operator via, for example, a human-machine interface, a speaker,or an external device (e.g., smartphone, cellular phone, tablet, laptopcomputer, desktop computer, and the like). As shown in FIG. 8, theelectronic processor 215 continues to monitor the proximity outputsignals at STEP 455 to continue to monitor the tension of the conveyor105.

FIG. 9 illustrates another embodiment 500 of the sensor assembly 205. Inthe illustrated embodiment 500, the sensor assembly 205 includes a firstproximity sensor 505 and a second proximity sensor 510. As shown in FIG.9, the first proximity sensor 505 has a first detection directionillustrated by arrow A, while the second proximity sensor 510 has asecond detection direction illustrated by arrow B. In the illustratedembodiment, the first detection direction is approximately perpendicularto the second detection direction. Similar to the proximity sensors415-440 of the second embodiment 400, the first and second proximitysensors 505, 510 are also energized as the first conveyor chain 120 (ora flightbar 150) is detected. Accordingly, the first and secondproximity sensors 505, 510 generate a binary output signal indicatingwhether the first conveyor chain 120 (or flightbar) is within adetection range of the sensors 505, 510.

In the illustrated embodiment, the first proximity sensor 505 detects avertical distance between the first proximity sensor 505 and the firstconveyor chain 120. The second proximity sensor 510 detects a horizontaldistance between the second proximity sensor 510 and the first conveyorchain 120. FIG. 9 illustrates an example of when the conveyor 105 isunder-tensioned and the first conveyor chain 120 is outside a firstdetection range 515 of the first proximity sensor 505 and outside asecond detection range 520 of the second proximity sensor 510.

When the embodiment 500 of the sensor assembly 205 is utilized, theelectronic processor 215 performs a method similar to method 450 shownin FIG. 8. For example, the electronic processor 215 receives the outputsignals from the first and second proximity sensors 505, 510 anddetermines, based on the combination of the output signals whether thefirst conveyor chain 120 is under-tensioned, over-tensioned, or withinan acceptable tension range. For example, as illustrated in FIG. 9, whenthe first and second proximity sensors 505, 510 generate a negative (ora null) signal, the electronic processor 215 determines that theconveyor 105 is under-tensioned. On the other hand, when only one of theproximity sensors 505, 510 generates a positive signal, the electronicprocessor 215 determines that the conveyor 105 is adequately tensioned.Finally, when both the first and second proximity sensors 505, 510generate a positive signal, the electronic processor 215 determines thatthe conveyor is over-tensioned. The electronic processor 215 may thenactivate the tensioning system when the conveyor 105 is outside theadequate tension range.

In some embodiments, the electronic processor 215 receives the proximityoutput signals using the sensor embodiment 400 or the sensor embodiment500 of the sensor assembly 205 and generates an estimated chaintrajectory based on the output signals from the various proximitysensors 415-440, 505, 510. FIGS. 10A-10D, for example, illustratevarious generated chain trajectories based on the output signals fromthe proximity sensors. Notably, the chain trajectory may also begenerated based on the output from the analog output sensor 310, or, insome embodiments, from a plurality of analog output sensors 310 usedtogether. FIG. 10A illustrates a generated chain trajectory in which thefirst conveyor chain 120 is over-tensioned and has a slack distance ofapproximately 0 mm. FIGS. 10B and 10C illustrate generated chaintrajectories in which the first conveyor chain 120 is properly tensionedand has a slack distance of 50 mm (FIG. 10B) and 100 mm (FIG. 10C),respectively. FIG. 10D illustrates a generated chain trajectory in whichthe first conveyor chain 120 is under-tensioned and has a slack distanceof approximately 150 mm. In embodiments in which the chain trajectory isgenerated, the electronic processor 215 may use the output signals fromthe proximity sensors 415-440, 505, 510 or the analog output sensor 310to generate the estimated chain trajectory, and may then determine theslack distance from the generated chain trajectory instead of directlyfrom the output sensor signals.

FIG. 11 illustrates another embodiment 600 of the sensor assembly 205.In the illustrated embodiment 600, the sensor assembly 205 includes afirst visual sensor 605. The visual sensor 605 may be, for example, alaser emitter/scanner, a LiDAR (light detection and ranging) sensor, acamera, and the like. Unlike the proximity sensors 415-440, 505, 510,and the analog output sensor 310 described above, the visual sensor 605captures image data. As shown in the illustrated embodiment, the visualsensor 605 is positioned near the first sprocket 132 and is directedtoward the first conveyor chain 120.

FIG. 12 is a flowchart illustrating a method 650 of maintaining theconveyor system 100 at an adequate tension using the fourth embodiment600 of the sensor assembly 205. In STEP 655, the electronic processor215 receives the image data from the visual sensor 605. The electronicprocessor 215 then identifies the first conveyor chain 120 in the imagedata captured by the visual sensor 605 (STEP 660). The electronicprocessor 215 utilizes several image processing techniques to identifythe conveyor chain 120 from the image data captured by the visual sensor605 such as, for example, shape recognition, straight edge detection,outlier detection, and the like. Based on the image data and theidentified conveyor chain 120, the electronic processor 215 thengenerates an estimated chain trajectory (STEP 665). The estimated chaintrajectory may be similar to, for example, those shown in FIGS. 10A-10D.In the illustrated embodiment, the electronic processor 215 proceeds tomeasure a slack distance from the estimated chain trajectory (STEP 670).In other words, the slack distance is measured from the virtualestimated chain trajectory rather than from the first conveyor chain 120itself. The electronic processor 215 then determines whether themeasured slack distance is within an acceptable range (STEP 675). Theacceptable range may be, for example, between 25-120 mm. Therefore, whenthe slack distance is lower than 25 mm or greater than 120 mm, theelectronic processor 215 determines that the slack distance is outsidethe acceptable range. When the slack distance is within the acceptablerange, the electronic processor 215 continues to receive the image datafrom the visual sensor 605 (STEP 655). Otherwise, when the slackdistance is outside the acceptable range, the electronic processor 215activates the tensioning system (STEP 680), and then continues toreceive the image data from the visual sensor 605 (STEP 655).

In some embodiments, the electronic processor 215 stores eachmeasurement regarding the tension of the conveyor 105 in a memory. Basedon the stored measurements, the electronic processor 215 may also beable to implement a trend analysis to identify when the conveyor 105 islikely to be outside the acceptable tension range. FIG. 13 is aflowchart illustrating an exemplary method 700 of analyzing previouslyacquired conveyor tension data to determine whether the conveyor 105 istrending toward being under-tensioned or over-tensioned. As shown inFIG. 13, the electronic processor 215 receives sensor signals from oneof the embodiments of the sensor assembly 205 described above (STEP705). The electronic processor 215 then stores the received sensorsignal (STEP 710). When implementing the trend analysis, the electronicprocessor 215 accesses previously stored sensor signals (STEP 715). Theelectronic processor 215 then determines a difference between thecurrent sensor signal and the previously stored sensor signal (STEP720). The electronic processor 215 proceeds to determine whether thedifference is greater than a predetermined amount (e.g., indicating thatthe slack distance has increased by more than, for example, 30 mm) atSTEP 725. When the electronic processor determines that the differenceis not greater than the predetermined amount, the electronic processorcontinues to receive the sensor signals as described in STEP 705. On theother hand, when the electronic processor 215 determines that thedifference is greater than the predetermined amount, the electronicprocessor activates the tensioning system 210 to prevent the conveyor105 to become under-tensioned or over-tensioned (STEP 730).

In one embodiment, the electronic processor 215 accesses sensor signalsassociated with the previous activations of the tensioning system 210.For example, the electronic processor 215 accesses the sensor signalsfor the previous five times that the tensioning system 210 wasactivated. The electronic processor 215 then identifies a patternassociated with the previous signals before the activation of thetensioning system 210. The electronic processor 215 then compares themost recently received sensor signals to the identified pattern. Whenthe most recently received sensor signals match the identified pattern,the electronic processor activates the tensioning system 210 to inhibitthe conveyor 105 from becoming under-tensioned or over-tensioned. Insome embodiments, the electronic processor 215 accesses previouslystored sensor signals and calculates a rate of change of the slackdistance. When the rate of change of the slack distance exceeds apredetermined threshold, the electronic processor 215 determines thatthe conveyor 105 is trending to become over-tensioned orunder-tensioned, and activates the tensioning system 210 to inhibit theconveyor 105 from becoming under-tensioned or over-tensioned.

In some embodiments, the electronic processor 215 may activate thetensioning system 210 before the conveyor 105 begins its operation suchthat the conveyor 105 starts at a predetermined (e.g., calibrated)tension. The electronic processor 215 may then evaluate the tensioncondition of the conveyor 105 as described above.

Accordingly, this application describes various sensors assemblies thatare used to determine a tension of a conveyor element (for example, aconveyor chain). The output signals and data from the sensor assembliesare utilized by the electronic processor to determine when to operatethe tensioning system such that the conveyor is maintained within anadequate tension range. Various features and advantages of the inventionare set forth in the following claims.

What is claimed is:
 1. A conveyor system, comprising: a sprocket; aconveyor element coupled to the sprocket to move around the sprocket,the conveyor element including a top-side portion on a top side of thesprocket and a bottom-side portion on an underside of the sprocket; asensor positioned adjacent to the sprocket between the top-side portionand the bottom-side portion of the conveyor element, the sensorconfigured to generate an output signal that varies proportionally to adistance between the sensor and the bottom-side portion of the conveyorelement; a tensioning system; and an electronic processor coupled to thesensor and to the tensioning system, the electronic processor configuredto receive the output signal from the sensor, determine a value forslack distance of the conveyor element based on the output signal, andcontrol the tensioning system based on the value for slack distance. 2.The conveyor system of claim 1, wherein the sensor is an analog distancesensor and a magnitude of the output signal varies proportionally to thedistance between the sensor and the bottom-side portion of the conveyorelement.
 3. The conveyor system of claim 2, wherein the sensor is atleast one selected from a group of an ultrasonic sensor, an infrared(IR) sensor, and a magnetometer.
 4. The conveyor system of claim 1,wherein, to control the tensioning system based on the value for slackdistance, the electronic processor is configured to: decrease a tensionin the conveyor element to prevent an over-tensioned condition when thevalue for slack distance is below a first threshold, and increase thetension in the conveyor element to prevent an under-tensioned conditionwhen the value for slack distance is above a second threshold.
 5. Theconveyor system of claim 1, wherein, to control the tensioning systembased on the value for slack distance, the electronic processor isconfigured to: determine a correction amount based on a differencebetween the value for slack distance and a threshold, where thecorrection amount is proportional to the difference, and control thetensioning system to change a tension of the conveyor element by anamount that is based on the correction amount.
 6. The conveyor system ofclaim 5, wherein, to control the tensioning system to change the tensionof the conveyor element by an amount that is based on the correctionamount, the electronic processor is configured to: set a timer having aduration corresponding to the correction amount, and activate thetensioning system for the duration of the timer to change the tension ofthe conveyor element.
 7. The conveyor system of claim 1, furthercomprising: a second sprocket; a second conveyor element coupled to thesecond sprocket to move around the second sprocket, the second conveyorelement including a second top-side portion on a top side of the secondsprocket and a second bottom-side portion on an underside of the secondsprocket; a second sensor positioned adjacent to the second sprocketbetween the second top-side portion and the second bottom-side portionof the second conveyor element, the second sensor configured to generatea second output signal that varies proportionally to a second distancebetween the second sensor and the second bottom-side portion of theconveyor element; and a second tensioning system; wherein the electronicprocessor is coupled to the second sensor and to the second tensioningsystem, the electronic processor configured to receive the second outputsignal from the second sensor, determine a second value for slackdistance of the second conveyor element based on the second outputsignal, and control the second tensioning system based on the secondvalue for slack distance.
 8. The conveyor system of claim 7, furthercomprising: a plurality of flight bars, each flight bar connectedbetween the conveyor element and the second conveyor element.
 9. Amethod for controlling tension in a conveyor element of a conveyorsystem that moves around a sprocket, the method comprising: generatingan output signal by a sensor positioned adjacent to the sprocket andbetween a top-side portion of the conveyor element on a top side of thesprocket and a bottom-side portion of the conveyor element on a bottomside of the sprocket, wherein the output signal from the sensor variesproportionally to a distance between the sensor and the bottom-sideportion of the conveyor element; receiving, at an electronic processor,the output signal from the sensor; determining, by the electronicprocessor, a value for slack distance based on the output signal; andcontrolling, by the electronic processor, a tensioning system based onthe value for slack distance.
 10. The method of claim 9, wherein thesensor is an analog distance sensor and a magnitude of the output signalvaries proportionally to the distance between the sensor and thebottom-side portion of the conveyor element.
 11. The method of claim 10,wherein the sensor is at least one selected from a group of anultrasonic sensor, an infrared (IR) sensor, and a magnetometer.
 12. Themethod of claim 9, wherein controlling the tensioning system based onthe value for slack distance includes: decreasing a tension in theconveyor element to prevent an over-tensioned condition when the valuefor slack distance is below a first threshold, and increasing thetension in the conveyor element to prevent an under-tensioned conditionwhen the value for slack distance is above a second threshold.
 13. Themethod of claim 9, wherein controlling the tensioning system based onthe value for slack distance includes: determining a correction amountbased on a difference between the value for slack distance and athreshold, where the correction amount is proportional to thedifference, and controlling the tensioning system to change a tension ofthe conveyor element by an amount that is based on the correctionamount.
 14. The method of claim 13, wherein controlling the tensioningsystem to change the tension of the conveyor element by an amount thatis based on the correction amount includes: setting a timer having aduration corresponding to the correction amount, and activating thetensioning system for the duration of the timer to change the tension ofthe conveyor element.
 15. The method of claim 9, wherein the conveyorsystem further includes a second conveyor element that moves around asecond sprocket, the method further comprising: generating a secondoutput signal by a second sensor positioned adjacent to the secondsprocket and between a second top-side portion of the second conveyorelement on a top side of the second sprocket and a second bottom-sideportion of the second conveyor element on a bottom side of the secondsprocket, wherein the second output signal from the second sensor variesproportionally to a second distance between the second sensor and thesecond bottom-side portion of the conveyor element; receiving, at theelectronic processor, the second output signal from the second sensor;determining, by the electronic processor, a second value for slackdistance based on the second output signal; and controlling, by theelectronic processor, a second tensioning system based on the secondvalue for slack distance.
 16. A controller for controlling tension in aconveyor element of a conveyor system that moves around a sprocket, thecontroller including a non-transitory computer readable medium and anelectronic processor, the controller comprising computer executableinstructions stored in the computer readable medium for controllingoperation of the conveyor system to: receive, at the electronicprocessor, an output signal from a sensor, wherein the sensor ispositioned adjacent to the sprocket and between a top-side portion ofthe conveyor element on a top side of the sprocket and a bottom-sideportion of the conveyor element on a bottom side of the sprocket,wherein the output signal from the sensor varies proportionally to adistance between the sensor and the bottom-side portion of the conveyorelement; determine, by the electronic processor, a value for slackdistance based on the output signal; and control, by the electronicprocessor, a tensioning system based on the value for slack distance.17. The controller of claim 16, wherein the sensor is an analog distancesensor and a magnitude of the output signal varies proportionally to thedistance between the sensor and the bottom-side portion of the conveyorelement.
 18. The controller of claim 16, wherein, to control thetensioning system based on the value for slack distance, the controllerfurther includes computer executable instructions stored in the computerreadable medium for controlling operation of the conveyor system to:decrease a tension in the conveyor element to prevent an over-tensionedcondition when the value for slack distance is below a first threshold,and increase the tension in the conveyor element to prevent anunder-tensioned condition when the value for slack distance is above asecond threshold.
 19. The controller of claim 16, wherein, to controlthe tensioning system based on the value for slack distance, thecontroller further includes computer executable instructions stored inthe computer readable medium for controlling operation of the conveyorsystem to: determine a correction amount based on a difference betweenthe value for slack distance and a threshold, where the correctionamount is proportional to the difference, and control the tensioningsystem to change a tension of the conveyor element by an amount that isbased on the correction amount.
 20. The controller of claim 19, wherein,to control the tensioning system to change the tension of the conveyorelement by an amount that is based on the correction amount, thecontroller further includes computer executable instructions stored inthe computer readable medium for controlling operation of the conveyorsystem to: set a timer having a duration corresponding to the correctionamount, and activate the tensioning system for the duration of the timerto change the tension of the conveyor element.